Messier 13, aka the Hercules Cluster, is a cluster of several hundred thousand stars in the constellation of Hercules.
During May, the length of darkness falls dramatically and quick sky navigation helps maximise your observing time. As an example, consider this route to find an object called Messier 13. First, locate the Plough or, as it’s also known, the Saucepan asterism (an asterism is an unofficial pattern), which is situated almost directly overhead as darkness falls in late May. Identify the three ‘handle’ stars furthest from the pan. Extend their arc away from the pan to arrive at the bright orange star, Arcturus.
!["Use]("https://images.immediate.co.uk/production/volatile/sites/4/2023/05/Use-guiding-stars-to-hop-from-the-Plough-to-M13-af09212.jpg?quality=90&resize=620%2C565" "\"Use")
Next, identify the star in the corner of the pan furthest from the handle. Extend a line from that corner star through the mid-point of the top of the pan (check the graphic above – it’s easier than it sounds). Keep going for two-and-a-half times the length of the Saucepan to arrive at bright, white-blue star, Vega.
A squashed-diamond pattern of stars hangs below, and is useful for confirming Vega’s identity.
One-third of the way from Arcturus towards Vega you’ll find the small, distinctive semi-circle of stars representing the Northern Crown, Corona Borealis. The brightest star is Gemma, the jewel in the crown.
Two-thirds of the way along the path that takes you from Arcturus to Vega, you’ll find the dim-yet-distinctive Keystone asterism, which is part of Hercules the Strongman. One-third of the way between the upper-right and lower-right stars in the Keystone, is a faint object that’s just visible to the naked eye under dark-sky conditions. Through binoculars, the object appears like a fuzzy star, but a telescope reveals a mass of stars in a concentrated clump.
!["Globular]("https://images.immediate.co.uk/production/volatile/sites/4/2023/05/Messier-13-is-located-in-the-constellation-Hercules-edbd060.jpg?quality=90&resize=620%2C399" "\"Star")
This is Messier 13, the Great Globular Cluster in Hercules. Messier 13 is estimated to contain several hundred thousand stars, all gravitationally bound into a spherical region of space 145 light-years across.
One light-year is the distance light travels in a year at the speed of 299,792,458 metres per second (or 186,000 miles every second).
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